Transformer



Sept. 14, 1926; 1,599,570

5. LUCAS TRANSFORMER Filed August 12 1922 WITNESSES: INVENTOR 8 m4 MMif; ATTORNEY Patented Sept. 14, 1926.

UNITED STATES PATENT OFFICE.

SAMUEL M. LUCAS, OF PITTSBURGH, YENNSYLVANIA, ASSIGNOR TO THE UNIONSWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPOBATION OFPENNSYLVANIA.

TRANSFORMER.

Application filed August 12, 1922. Serial No. 581,398.

My invention relates to electrical transformers, and has for an objectthe provision of a transformer which will deliver a subslantiallyconstant voltage to the secondary A! circuit under wide variations inthe voltage applied to the primary.

I will describe two forms of transformers embodying my invention, andwill then point out the novel features thereof in claims.

In the accompanying drawing, 'Fig. 1 is a view showing one form oftransformer embodying my invention, and Fig. 2 is a view showing amodified form of transformer also embodying my invention.

Similar reference characters refer similar parts in each of the views.

Referring first to Fig. 1, the transformer comprises a core (l ofmagnetizable material, provided with a primary winding 1" and asecondary winding S. The portion of the core 0 which carries thesecondary winding S is so designed that it is magnetically saturated atthe normal voltage 26 applied to the transformer, and in practice it ispreferably saturated at some applied voltage less than the normalvoltage. The transformer also comprises a member I) of magnetizablematerial which forms a shunt 80 around the portion C of thecore C, thismember being separated from the core by air gaps 10. This member I)constitutes a magnetic leakage path in multiple with the saturated pathG, and the air gaps '10 are 85 such as to force suflicient flux throughthe saturated path to saturate it at all applied voltages under normalvoltage and down to a predetermined minimum.

The primary winding P is, of course,

40 connected with a source of alternating current and the secondarywinding S is connected with a current-consuming device which, as hereshown, is an electric lamp 12.

Assuming that the voltage applied to the 46 primary winding P is theqredetermined. minimum referred to above, t ie portion U of core C willbe saturated so that the normal amount of current will be delivered tothe lamp 12. As the voltage applied to the I) primary winding I rises,the total magnetic flux due to this winding will increase, but all ofthe flux in excess of that required to saturate the core member C will'pass through the leakage member D, so that the voltage supplied to thelamp 12 will remain substantially constant.

Referring now to Fig. 2, the transformer shown in this View. is the sameas that shown in Fig. 1, except that the leakage member D is providedwith an auxiliary winding 11 of a few turns, which turns are included inseries with the secondary S in the circuit for lamp 12. With thisarrangement, the core member C is preferably so designed that at normalvoltage it is not completely saturated, so that the voltage induced insecondary S will vary with the variations in the voltage applied to theprimary l. The variations 1n the secondary voltage will be in the samedirection as the variations in the primary voltage, but will beconsiderably smaller in degree. The voltage induced in the auxiliarywinding 11, however, varies at a greater rate than the primary voltage,and inasmuch as the voltage of the auxiliary winding opposes that of thesecondary winding the voltage applied to lamp 12 can bekeptsubstantially constant-even though the core member C" is not operated atcomplete saturation.

Transformers embodying my invention are particularly well adapted forrailway signaling systems comprising light signals, which signals areusually supplied from an alternating current transmission line throughstep-down transformers. On account of the fact that a small drop involtage causes a large decrease in the candle power of the signal lamps,it is necessary to limit this drop to a small value, and this makes itnecessary to apply a comparatively high voltage to the transmission linein order to avoid dropping below the permissive voltage at the lamps. Byusing transformers embodying my invention in a system of this nature,the voltage applied to the lamp can be kept substantially constant inspite of the variations in the line voltage of the transmission line.The watt efiicieney of the transformers shown in Figs. 1 and 2 is fairlygood, but due to a rather large magnetizing current the volt-ampereefiicieney is low. This can be greatly improved by connecting acondenser 14 across the terminals of the primary winding P as shown inFig. 1, or b connecting this condenser with a third win ing 13 on thecore C, as shown in Fig. 2.

Although I have herein shown and described only two'forms oftransformers embodying my invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of myinvention. I

Having thus described my invention, what I claim is:

1. In combination, a transformer comprising a magnetizable core having apart of reduced cross-sectional area, a secondary winding on saidreduced part of the core and a primary winding on another part of thecore, a magnetic leakage member shunting the reduced part of said core,and an auxiliary winding on said leakage member;

and an electro-responsive device connected with said secondary windingand said auxiliary winding in such manner that the voltages supplied tothe device by the windings are in opposition; the parts being soadjusted that as the voltage applied to said primary winding rises abovethe normal value the voltage applied to said electro-responsive deviceremains substantially constant.

2. In combination, a transformer comprising a magnetizable core having apart of reduced cross-sectional area that is magnetically saturated at avoltage above normal, a secondary winding on said reduced part and aprimary winding on another part of said core, a magnetic leakage membershunting the reduced part of said core, and an auxiliary Winding on saidleakage member; and an electro-responsive device connected with saidsecondary winding and said auxiliary winding in such manner than thevoltages supplied to the device by the windings are in opposition; theparts being so adjusted that as the voltage applied to said primarwinding rises above the normal value t e voltage applied to saidelectro-responsive device remains substantially constant.

3. In combination, a transformer comprising a magnetizable core, aprimary and a secondary winding on said core, a magnetic leakage membershunting the part of said core which carries said secondary winding andan auxiliary winding on said leakage member; and an electro-responsivedevice connected with said secondary winding and said auxiliary windingin such manner that the voltages supplied to the device by the windingsare in opposition; the parts being so adjusted that as the voltageapplied to said primary winding rises above the normal value the voltageapplied to said electroresponsive device remains substantially constant.

4. In combination, a. transformer comprising a magnetizable core havinga part of reduced cross-sectional area, a secondary winding on saidreduced part of the core and a primary winding on another part of thecore, a third winding on said core, a condenser connected with saidthird winding, a magnetic leakage member shunting the reduced part ofsaid core, and an auxiliary winding on said leakage member; and ane1ectro-responsive device connected with said secondary winding and saidauxiliary winding in such manner that the voltages supplied to thedevice by the windings are in opposition; the parts being so adjustedthat as the voltage applied to said primary winding rises above thenormal value the voltage applied to said electro-responsive deviceremains substantially constant.

In testimony whereof I afiix my signature.

SAMUEL M. LUCAS.

